﻿using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace ProjectEulerSolutions
{
    /*
     * Starting with 1 and spiralling anticlockwise in the following way, a square spiral with side length 7 is formed.

37 36 35 34 33 32 31
38 17 16 15 14 13 30
39 18  5  4  3 12 29
40 19  6  1  2 11 28
41 20  7  8  9 10 27
42 21 22 23 24 25 26
43 44 45 46 47 48 49

It is interesting to note that the odd squares lie along the bottom right diagonal, but what is more interesting is that 8 out of the 13 numbers lying along both diagonals are prime; that is, a ratio of 8/13 ≈ 62%.

If one complete new layer is wrapped around the spiral above, a square spiral with side length 9 will be formed. If this process is continued, what is the side length of the square spiral for which the ratio of primes along both diagonals first falls below 10%?

     * */
    class Problem58 : IProblem
    {
        public string Calculate()
        {
            SieveOfAtkin sieve = new SieveOfAtkin(100000000);


            int step = 0;
            int count = 1;
            int primeCount = 0;
            int n = 1;
            double omjer = 0;

            do
            {
                step += 2;
                n += step;
                if (sieve.IsPrime(n))
                    primeCount++;
                n += step;
                if (sieve.IsPrime(n))
                    primeCount++;
                n += step;
                if (sieve.IsPrime(n))
                    primeCount++;
                n += step;

                count += 4;

                omjer = primeCount / (double)count;

            } while (omjer > 0.1);


            return (step + 1).ToString(); ;
        }
    }
}
